Entrance to the tunnel Union forces dug in an
attempt to undermine a Confederate salient and blow it up. The plan was
initially suggested by a Union soldier who had been a coal miner before the
war. It took the miners about a month to dig the 511 foot and the 2 side
galleries. The Confederates were guessed the Union intent and dug a couple
of countermines, narrowly missing one of the galleries. At the last minute
the plan was changed to send several regiments of white soldiers (instead of
the US Colored troops) who had trained for the mission. The explosion
created the crater as planned, but the untrained troops rushed down into the
crater instead of going around. The sides were very steep and the troops
were trapped in the crater and most were killed or captured by the rebels
when they got their wits together

(5-2001) Petersburg National
Battlefield Tour Stop-8: The Crater

Another
view of the tunnel entrance with me (Jack Snyder) standing beside it for
scale

(5-2001) Petersburg National
Battlefield Tour Stop-8: The Crater

Close-up of tunnel entrance, shot thru the
bars showing NPS artistic endeavors. Note Hardtack Box with handles used to
carry out the dirt for disposal away from the entrance and out of the rebels
view. For ventilation a smaller vertical shaft was dug approximately 100
feet or so into the tunnel. A fire was kept burning there and the rising hot
air created a draft in the tunnel keeping the miners supplied with fresh air